The present invention relates to a vehicle control system and more particularly to a new and improved vehicle drive and steering system.
Typically in so called all terrain vehicles two drive trains having a series of sprocket and chain assemblies or the like on each side of the vehicle are used independently to control wheels or tracks on opposite sides of the vehicle. Power to the separate drive trains is typically controlled by a pair of drive control levers, wherein one lever controls the wheels on one side of the vehicle and the other lever controls the wheels on the other side of the vehicle. Normally, moving a lever forward causes the wheels on that respective side to turn, and moving the lever rearwardly causes the wheels on that respective side to brake. A central position of the lever is neutral and has no effect on the wheels. Consequently, such a prior art vehicle control is used to cause the vehicle to move forwardly when the gear box is turning forward by moving both levers forwardly, turn to the left by moving the left lever back while holding the right lever forward, and turn right by moving the left lever forward and the right lever back. This operational pattern of the levers has been used for many years and operators of such vehicles have become accustomed to this type of steering system.
Many prior art vehicles of this type have utilized a separate power supply or engine for each side of the vehicle. An early example of such an apparatus is shown in Parker U.S. Pat. No. 1,430,251 which discloses an engine on each side of a four wheel tractor, with the engine being connected to respective wheels by a chain and sprocket drive system. Steering is accomplished by connecting power on one side of the vehicle to its respective wheels while disconnecting power on the opposite side to its respective wheels. A similar type of vehicle is disclosed in Shanahan et al U.S. Pat. No. 3,204,713, which utilizes a single power supply that is divided through separate drive trains to wheels on opposite sides of the vehicle and utilizes simultaneous braking on one side of the vehicle and wheel rotation on the other side of the vehicle to accomplish steering.
Rhoades U.S. Pat. No. 2,605,852 shows a vehicle having two separate electrical motors for each side of the vehicle and arranged in series across a power supply. Brakes are applied to the motor on one side of the vehicle which automatically speeds up the motor on the other side to accomplish steering. Rilling U.S. Pat. No. 3,616,869 utilizes a power supply to develop power through two hydraulic motors, one for each side of the vehicle, wherein the wheels on opposite sides of the vehicle are run at unequal speeds in order to accomplish steering. All of the above described systems offer various apparent disadvantages, but in the more modern steering control systems, the main drawbacks, aside from not providing positive steering of the vehicle are that such systems are complicated, and thus more expensive. In addition the utilization of separate power supplies for separate drive trains to accomplish steering is costly to build, maintain and operate. All terrain vehicles are usually used in remote locations where fuel supplies, maintenance etc., are difficult to obtain, thus making fuel economy and system simplicity important operational factors.
A more positive method of steering such vehicles is provided by turning the wheels or tracks on the opposite sides of the vehicle in opposite directions. Odom U.S. Pat. No. 2,542,157 shows such a system. One power supply is used to transmit power through a split drive train to track mechanism on opposite sides of the vehicles. The Odom system utilizes three control levers for controlling the drive and steering functions of the vehicle. Odom for the most part, uses positively connected transfer devices such as intermeshing bevel gears to transmit power and motion through the drive train, which on all terrain vehicles is a disadvantage. Because of the excessive roughness to which such equipment is subjected in its normal use, it is extremely important to utilize power transmission devices that have a give or slack so that sudden forces applied to the power drive system do not cause excessive fatigue to the mechanisms transmitting the motion and power.
It is therefore an object of the present invention to provide a new and improved drive and steering apparatus for an all terrain vehicle which will accomplish positive steering by providing means for rotating wheels on opposite sides of the vehicle in opposite directions, and which, by sufficiently simple design and construction will provide for low initial cost, minimize maintenance, accommodate the wear and tear of the hazardous environment in which such vehicles are operated, and utilize a traditional steering system to which operators of such vehicles have become accustomed.